The Earth is under constant threat of attack. I know this because I am watching events unfold on screens in the darkened operations room of our first line of defence.

Staffed 24 hours a day, 365 days a year, the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center in Boulder, Colorado resembles the bridge of the Starship Enterprise. The walls are covered in TV screens, displaying live images of the Sun captured by telescopes and spacecraft. Two men sit at curved desks in front of me, each surrounded by a bank of computer monitors. Their faces are lit by the dancing reflections of our nearest star in a range of spectra, through blue to red and dazzling white. One of them is taking a particular interest in a dark patch on the left side of the Sun, displayed as a bleached-out image on one of his screens.

“All these images are daunting, a bit like the Louvre for space weather,” says my guide, space scientist Joe Kunches.

Space weather refers to everything the Sun throws at us – from the continuous stream of charged particles it constantly spews out, called the solar wind, to the belches of eruptions, ejections and flares. The Earth is protected from this onslaught, to a large extent, by its magnetic field, which generates a shield or bubble around the planet known as the magnetosphere.

But what forecasters at the centre are watching out for is a particularly violent solar event: for instance, a geomagnetic storm that could penetrate the Earth’s natural defences, causing surges in electricity grid and disrupting power supplies; a radiation storm that bombards orbiting astronauts with a lethal dose of high energy particles; or radio interference that renders aircraft communications or GPS useless.

This year is supposed to be the year of the solar maximum, the peak of the 11-year sunspot cycle. Yet this maximum has turned out to be a weak one so far, sunspot numbers and strong solar flares have been far below predicted values.

The solar max may have failed to live up to its violent billing up until now, but no-one here is complacent – hence the interest in the dark patch slowly evolving on the Sun, signifying a cluster of sunspots the size of our planet. “We want to understand where eruptions are most likely to occur,” says Kunches, “and in doing that, we look for strong magnetic fields and hotspots in the solar atmosphere.” By examining the conditions today, they can make decisions about the likelihood of an eruption. Then they need to decide whether that eruption is coming our way and, if it is, how strong it is going to be.

The centre issues daily advisory notices based on a five-point scale ranging from minor to extreme. This information is coordinated with other national space weather services and shared with governments. It is used by airlines, space agencies, satellite operators and power companies. Airlines flying over the poles for instance, where the magnetosphere is weaker, have specific thresholds for solar activity and may choose to alter flight paths to avoid exposing their passengers and crew to a dangerous dose of radiation. Satellite operators could decide to power-down their spacecraft to protect them. Electricity companies might prepare for overloads. Those solar events predicted as extreme will go as far as emergency planning agencies and even the White House.

So what’s the worst the Sun could throw at us? The event that goes down in the relatively brief history of space weather watching is a solar super storm of 1859. Now known as the Carrington Event after British astronomer Richard Carrington who first spotted it, this lit up the skies across the world with stunning aurorae. Electrical surges induced in the Earth’s magnetic field were reportedly sufficient to power the telegraph system without batteries. Some telegraph operators spoke of sparks flying from their equipment. It was all very dramatic but, other than some interference with Victorian communications, there were no long-term effects.

Storm alert

A similar event today, with our dependence on electrical and electronic technology, would have much bigger consequences. “The potential impacts on the nation – and the globe – has caught the attention of government leadership around the world,” says NOAA’s Space Weather Program Coordinator, Bill Murtagh. He spends much of his time trying to convince policy makers to give space weather the attention he feels it deserves. As well as warning about the relatively short-term loss of GPS, global communications and other satellite services, there is growing concern that a major solar storm could change civilisation as we know it.

“The impact on the electric power grid could be catastrophic,” Murtagh says. “It could result in a widespread blackout, extending not just hours, days or weeks, but maybe months or years.”

Murtagh is quick to deny that this is scaremongering. He explains that space weather forecasters are concerned about a weak link in global infrastructure: transformers, in power and substations around the world. “Picture what would happen if we damage some of our big transformers – some of them are as big as houses, and they are tailor-made in large part as well. To get them replaced would take an extended period of time,” he warns. “The impact could be long term.”

So how likely is a major solar event? It will certainly happen, but at the moment, no one knows when. It could be next week, next year, or not for another hundred or thousand years. At the time of writing, two coronal mass ejections, or CMEs, are heading towards Earth, which officials stress do not pose a threat but could possibly spark geomagnetic storms around the poles. Although the set-up at the Space Weather Prediction Center looks very impressive, the science of predicting solar activity is still in its infancy. Observers here have good live data of the Sun from telescopes and several space science missions – such as Nasa’s twin Solar Terrestrial Relations Observatory (Stereo) spacecraft, the aging Advanced Composition Explorer (Ace) satellite, or the international Solar and Heliospheric Observatory (Soho) – but none of them were specifically designed for forecasting space weather. In fact several have already exceeded their design life.

What this means is that long-term forecasts, beyond the next few hours, are currently of limited reliability. Certainly not good enough for power companies to risk the massive economic consequences of shutting down their network on the off-chance they might be hit, or investing in warehouses full of replacement transformers that may never get used.

Right now, if a large solar flare or coronal mass ejection from an eruption on the Sun’s surface does come our way, forecasters will see it but there will not be much time to react. “In some cases it’s too late,” admits Kunches. “Photons – the light from that eruption – have already got here, because you can’t beat the speed of light,” he says. “So high-frequency radio has already been disrupted. By the time we tell them, they already know it.”

Close behind, travelling at almost the speed of light, will be high-energy radiation, giving astronauts on the International Space Station only around ten to fifteen minutes to seek shelter in the specially shielded sections. For anyone on a spacewalk, that may not be enough. Veterans of the Apollo missions, travelling outside the Earth’s protective magnetosphere, admit they were lucky to have escaped this threat.

“Fortunately,” says Kunches, “our largest customer base is affected by geomagnetic storm activity – the power grids, other aspects of satellite operations, pipelines and the general public who want to see brilliant auroras – because those CMEs take longer to get here, they may get 12 hours notice.”

As the drama of the sunspot cluster unfolds on the screens, it is sobering to think of the possible consequences. The chances are that this cluster fails to produce any solar flares, or if it does the flares are flung out away from our planet. But all it takes is one that could develop into a major event and do lasting damage to the technology we rely on every day. And if that happens, as things stand, we may only have 12 hours to do anything about it.

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